In the state of the art there is a wide selection of pedicle screws with closure devices having, as a rule, a receiving part with a U-shaped recess for receiving a rod, which recess has between its free arms an internal threading for accepting a screw for fixing the rod.
U.S. Pat. No. 5,496,321 describes a pedicle screw with an anchoring means. This product has the disadvantage, however, that the anchoring means has to be inserted in the screw head in the direction of the rod, which, in the case of small radii of curvature of the rod, can lead to considerable difficulties under operating conditions.
U.S. published patent application No. 2003/0004511 describes a pedicle screw system, whose receiving arms for a rod are connected with a hinge. After receiving the rod, the receiving arms are provided with a closure cap or a closure yoke, which press the arms together and hold the rod firmly. To put on the closure cap or yoke, the arms of the head of the pedicle screw have to be pressed together, and at the same time the closure piece has to be pushed in the rod direction or turned, or repetitively the closure yoke has to be pushed in the rod direction or turned, or respectively the closure yoke has to be hung, requiring not only considerable skill on the part of the operator, but, depending upon the embodiment, also a special instrument.